1. Field of the Invention
The present invention relates to an optical element having a transparent substrate composed of, for example, glass and a lens portion formed on a surface of the transparent substrate, and particularly, to an optical element additionally having a light-blocking film formed on the surface of such a transparent substrate.
2. Description of the Related Art
As an example of an optical element having a lens portion used in cameras or the like, an optical element that includes a transparent substrate composed of, for example, glass or resin and a lens portion formed on a surface of the transparent substrate is known. The lens portion generally has a lens-functioning surface and thus has a light focusing function. It is also known that an ultraviolet curable resin is a suitable material for forming multiple lens portions of this type efficiently in an array on a transparent substrate.
In such a case, the lens portions are formed in the following manner. First, uncured ultraviolet curable resin is placed on the transparent substrate. Then, a die is placed over the ultraviolet curable resin from above the transparent substrate, and is pressed so that the ultraviolet curable resin is spread within the space between the transparent substrate and the die. Subsequently, ultraviolet light is emitted towards the ultraviolet curable resin through the transparent substrate, causing the ultraviolet curable resin to become cured. As a result, lens portions are formed. An example of such a method for forming lens portions is disclosed in Japanese Unexamined Patent Application Publication No. 2002-355826.
An optical element having a transparent substrate and a lens portion formed thereon is also generally equipped with a light-blocking film on the transparent substrate, which serves as an aperture stop for the lens portion. Such a light-blocking film has a circular opening having a predetermined diameter and is attached to a surface of the transparent substrate. The lens portion is disposed on the light-blocking film such that the lens-functioning surface of the lens portion covers the opening. This allows the opening of the light-blocking film to function as an aperture stop for the lens portion.
However, with the outer edge of the lens portion being located close to the opening of the light-blocking film, the light coming in through the outer edge or light reflected at the outer edge can unfavorably pass through the opening of the light-blocking film functioning as an aperture stop. This can sometimes produce lens flare or ghost on the image obtained by the optical element.